Use of triarylamine derivatives as hole-conducting materials in organic solar cells and organic solar cells containing said triarylamine derivatives

ABSTRACT

The present invention relates to the use of compounds of the general formula I 
     
       
         
         
             
             
         
       
     
     in which
     A 1 , A 2 , A 3  are each independently divalent organic units which may comprise one, two or three optionally substituted aromatic or heteroaromatic groups, where, in the case of two or three aromatic or heteroaromatic groups, two of these groups in each case are joined to one another by a chemical bond and/or via a divalent alkyl radical,   R 1 , R 2 , R 3  are each independently R, OR, NR 2 , A 3 -OR or A 3 -NR 2  substituents,   R is alkyl, aryl or a monovalent organic radical which may comprise one, two or three optionally substituted aromatic or heteroaromatic groups, where, in the case of two or three aromatic or heteroaromatic groups, two of these groups in each case are joined to one another by a chemical bond and/or via a divalent alkyl or NR′ radical,   R′ is alkyl, aryl or a monovalent organic radical which may comprise one, two or three optionally substituted aromatic or heteroaromatic groups, where, in the case of two or three aromatic or heteroaromatic groups, two of these groups in each case are joined to one another by a chemical bond and/or via a divalent alkyl radical,
       and   
       n at each instance in formula I is independently 0, 1, 2 or 3,
       with the proviso that the sum of the individual values n is at least 2 and at least two of the R 1 , R 2  and R 3  radicals are OR and/or NR 2  substituents,
 
as hole-conducting materials in organic solar cells.
   
       

     The present invention further relates to organic solar cells which comprise these compounds.

The present invention relates to the use of compounds of the generalformula I

-   in which-   A¹, A², A³ are each independently divalent organic units which may    comprise one, two or three optionally substituted aromatic or    heteroaromatic groups, where, in the case of two or three aromatic    or heteroaromatic groups, two of these groups in each case are    joined to one another by a chemical bond and/or via a divalent alkyl    radical,-   R¹, R², R³ are each independently R, OR, NR₂, A³-OR or A³-NR₂    substituents,-   R is alkyl, aryl or a monovalent organic radical which may comprise    one, two or three optionally substituted aromatic or heteroaromatic    groups, where, in the case of two or three aromatic or    heteroaromatic groups, two of these groups in each case are joined    to one another by a chemical bond and/or via a divalent alkyl or NR′    radical,-   R′ is alkyl, aryl or a monovalent organic radical which may comprise    one, two or three optionally substituted aromatic or heteroaromatic    groups, where, in the case of two or three aromatic or    heteroaromatic groups, two of these groups in each case are joined    to one another by a chemical bond and/or via a divalent alkyl    radical,    -   and-   n at each instance in formula I is independently 0, 1, 2 or 3,    -   with the proviso that the sum of the individual values n is at        least 2 and at least two of the R¹, R² and R³ radicals are OR        and/or NR₂ substituents,        as hole-conducting materials in organic solar cells.

The present invention further relates to organic solar cells whichcomprise these compounds.

Dye solar cells (“DSCs”, or dye-sensitized solar cells, “DSSCs”; theseterms and abbreviations are used synonymously hereinafter) are one ofthe most efficient alternative solar cell technologies at present. In aliquid variant of this technology, efficiencies of up to 11% have beenachieved to date (e.g. Grätzel M. et al., J. Photochem. Photobio. C,2003, 4, 145; Chiba et al., Japanese Journal of Appl. Phys., 2006, 45,L638-L640).

The construction of a DSC is generally based on a glass substrate, whichis coated with a transparent conductive layer, the working electrode. Ann-conductive metal oxide is generally applied to this electrode or inthe vicinity thereof, for example an approx. 10-20 μm-thick nanoporoustitanium dioxide layer (TiO₂). On the surface thereof, in turn, amonolayer of a light-sensitive dye, for example a ruthenium complex, istypically adsorbed, which can be converted to an excited state by lightabsorption. The counterelectrode may optionally have a catalytic layerof a metal, for example platinum, with a thickness of a few μm. The areabetween the two electrodes is filled with a redox electrolyte, forexample a solution of iodine (I₂) and lithium iodide (LiI).

The function of the DSC is based on the fact that light is absorbed bythe dye, and electrons are transferred from the excited dye to then-semiconductive metal oxide semiconductor and migrate thereon to theanode, whereas the electrolyte ensures that the charges are balanced viathe cathode. The n-semiconductive metal oxide, the dye and the (usuallyliquid) electrolyte are thus the most important constituents of the DSC,though cells comprising liquid electrolyte in many cases suffer fromnonoptimal sealing, which leads to stability problems. Various materialshave therefore been studied for their suitability as solidelectrolytes/p-semiconductors.

For instance, various inorganic p-semiconductors such as CuI,CuBr.3(S(C₄H₉)₂) or CuSCN have found use to date in solid-stage DSCs.With CuI- or CuSCN-based, solid DSCs, for example, efficiencies of up to3% have been reported (Tennakone et al. J. Phys. D: Appl. Phys, 1998,31, 1492; O'Regan et al. Adv. Mater 200, 12, 1263; Kumara et al. Chem.Mater. 2002, 14, 954).

Organic polymers are also used as solid p-semiconductors. Examplesthereof include polypyrrole, poly(3,4-ethylenedioxythiophene),carbazole-based polymers, polyaniline, poly(4-undecyl-2,2′-bithiophene),poly(3-octylthiophene), poly(triphenyldiamine) andpoly(N-vinylcarbazole). In the case of poly(N-vinylcarbazole), theefficiencies reach up to 2%; with a PEDOT(poly(3,4-ethylenedioxythiophene), polymerized in situ, an efficiency of2.9% was even achieved (Xia et al. J. Phys. Chem. C 2008, 112, 11569),though the polymers are typically not used in pure form but usually in amixture with additives. In addition, a concept in which polymericp-semiconductors are bonded directly to an Ru dye is also presented(Peter, K., Appl. Phys. A 2004, 79, 65).

The highest efficiencies to date are, however, achieved with lowmolecular weight organic p-semiconductors. For example, avapor-deposited layer of triphenylamine (TPD) was applied as areplacement for the liquid electrolyte to the dye-sensitized layer. Theuse of the organic compound2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenyl-amine)-9,9′-spirobifluorene(spiro-MeOTAD) in dye solar cells was reported in 1998. The methoxygroups adjust the oxidation potential of the spiro-MeOTAD such that theRu complex can be regenerated efficiently. In the case of use ofspiro-MeOTAD alone as a p-conductor, a maximum IPCE (incident photon tocurrent conversion efficiency, external photon conversion efficiency) of5% is achieved. With addition of N(PhBr)₃SbCl⁶ (as a dopant) andLi[(CF₃SO₂)₂N], a rise in the IPCE to 33%, and in the efficiency to0.74%, was observed. The addition of tert-butylpyridine enhanced theefficiency to 2.56%, with an open-circuit voltage (V_(oc)) of approx.910 mV and a short-circuit current I_(SC) of approx. 5 mA measured at anactive area of approx. 1.07 cm² (Krüger et al., Appl. Phys. Lett., 2001,79, 2085). Dyes which achieve better coverage of the TiO₂ layer andwhich have good wetting on spiro-MeOTAD exhibit efficiencies of morethan 4% (Schmidt-Mende et al., Adv. Mater. 17, p. 813-815 (2005)). Evenbetter efficiencies of 5.1% are observed when a ruthenium complex withoxyethylene side chains is used (Snaith, H. et al., Nano Lett., 7,3372-3376 (2007)).

Durrant et al., Adv. Func. Mater. 2006, 16, 1832-1838 state that, inmany cases, the photocurrent is directly dependent on the yield in thehole transition from the oxidized dye to the solid p-conductor. Thisdepends essentially on two factors: first on the degree of penetrationof the p-semiconductor into the oxide pores, and second on thethermodynamic driving force for the charge transfer, i.e. especially onthe difference in the free enthalpy ΔG between dye and p-conductor.

Currently the best efficiencies in DSCs with solid hole conductors areobtained with the compound spiro-MeOTAD already mentioned above, thechemical formula of which is shown below:

(Snaith, H. J.; Moule, A. J.; Klein, C.; Meerholz, K.; Friend, R. H.;Gratzel, M. Nano Lett.; (Letter); 2007; 7(11); 3372-3376)

Studies by C. Jäger et al. (Proc. SPIE 4108, 104-110 (2001)) show thatthis compound is present in semicrystalline form, and there is thus therisk that it will (re)crystallize in the processed form, i.e. in theDSC.

In addition, the solubility in customary process solvents is relativelylow, which leads to a correspondingly low degree of pore filling.

It was therefore an object of the present invention to provide furthercompounds which can be used advantageously as p-semiconductors in solarcells, especially in DSCs. With regard to their profile of properties,these compounds should have good hole-conducting properties, have only avery low tendency, if any, to crystallize, and have good solubility inthe solvents used customarily, in order to bring about a maximum degreeof filling of the oxide pores.

Accordingly, the use of the compounds cited at the outset in organicsolar cells, and organic solar cells comprising these compounds, havebeen found.

Alkyl is understood to mean substituted or unsubstituted C₁-C₂₀-alkylradicals. Preference is given to C₁- to C₁₀-alkyl radicals, particularpreference to C₁- to C₈-alkyl radicals. The alkyl radicals may be eitherstraight-chain or branched. In addition, the alkyl radicals may besubstituted by one or more substituents selected from the groupconsisting of C₁-C₂₀-alkoxy, halogen, preferably F, and C₆-C₃₀-arylwhich may in turn be substituted or unsubstituted. Examples of suitablealkyl groups are methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl andoctyl, and also derivatives of the alkyl groups mentioned substituted byC₆-C₃₀-aryl, C₁-C₂₀-alkoxy and/or halogen, especially F, for exampleCF₃. Examples of linear and branched alkyl radicals are methyl, ethyl,propyl, butyl, pentyl, hexyl, heptyl and octyl, and also isopropyl,isobutyl, isopentyl, sec-butyl, tert-butyl, neopentyl,3,3-dimethylbutyl, 2-ethylhexyl.

Divalent alkyl radicals in the A¹, A², A³, R, R′, R⁴, R⁵, R⁶, R⁷, R⁸ andR⁹ units derive from the aforementioned alkyl by formal removal of afurther hydrogen atom.

Suitable aryls are C₆-C₃₀-aryl radicals which are derived frommonocyclic, bicyclic or tricyclic aromatics and do not comprise any ringheteroatoms. When the aryls are not monocyclic systems, in the case ofthe term “aryl” for the second ring, the saturated form (perhydro form)or the partly unsaturated form (for example the dihydro form ortetrahydro form), provided the particular forms are known and stable, isalso possible. The term “aryl” in the context of the present inventionthus comprises, for example, also bicyclic or tricyclic radicals inwhich either both or all three radicals are aromatic, and also bicyclicor tricyclic radicals in which only one ring is aromatic, and alsotricyclic radicals in which two rings are aromatic. Examples of arylare: phenyl, naphthyl, indanyl, 1,2-dihydronaphthenyl,1,4-dihydronaphthenyl, fluorenyl, indenyl, anthracenyl, phenanthrenyl or1,2,3,4-tetrahydronaphthyl. Particular preference is given toC₆-C₁₀-aryl radicals, for example phenyl or naphthyl, very particularpreference to C₆-aryl radicals, for example phenyl.

Aromatic groups in the A¹, A², A³, R, R′, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹units derive from the aforementioned aryl by formal removal of one ormore further hydrogen atoms.

Heteroaromatic groups in the A¹, A², A³, R, R′, R⁴, R⁵, R⁶, R⁷, R⁸ andR⁹ units derive from hetaryl radicals by formal removal of one or morefurther hydrogen atoms.

The parent hetaryl radicals here are unsubstituted or substituted andcomprise 5 to 30 ring atoms. They may be monocyclic, bicyclic ortricyclic, and some can be derived from the aforementioned aryl byreplacing at least one carbon atom in the aryl base skeleton with aheteroatom. Preferred heteroatoms are N, O and S. The hetaryl radicalsmore preferably have 5 to 13 ring atoms. The base skeleton of theheteroaryl radicals is especially preferably selected from systems suchas pyridine and five-membered heteroaromatics such as thiophene,pyrrole, imidazole or furan. These base skeletons may optionally befused to one or two six-membered aromatic radicals. Suitable fusedheteroaromatics are carbazolyl, benzimidazolyl, benzofuryl, dibenzofurylor dibenzothiophenyl. The base skeleton may be substituted at one, morethan one or all substitutable positions, suitable substituents being thesame as have already been specified under the definition of C₆-C₃₀-aryl.However, the hetaryl radicals are preferably unsubstituted. Suitablehetaryl radicals are, for example, pyridin-2-yl, pyridin-3-yl,pyridin-4-yl, thiophen-2-yl, thiophen-3-yl, pyrrol-2-yl, pyrrol-3-yl,furan-2-yl, furan-3-yl and imidazol-2-yl and the correspondingbenzofused radicals, especially carbazolyl, benzimidazolyl, benzofuryl,dibenzofuryl or dibenzothiophenyl.

Possible further substituents of the one, two or three optionallysubstituted aromatic or heteroaromatic groups include alkyl radicals,for example methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl andoctyl, and also isopropyl, isobutyl, isopentyl, sec-butyl, tert-butyl,neopentyl, 3,3-dimethylbutyl and 2-ethylhexyl, aryl radicals, forexample C₆-C₁₀-aryl radicals, especially phenyl or naphthyl, mostpreferably C₆-aryl radicals, for example phenyl, and hetaryl radicals,for example pyridin-2-yl, pyridin-3-yl, pyridin-4-yl, thiophen-2-yl,thiophen-3-yl, pyrrol-2-yl, pyrrol-3-yl, furan-2-yl, furan-3-yl andimidazol-2-yl, and also the corresponding benzofused radicals,especially carbazolyl, benzimidazolyl, benzofuryl, dibenzofuryl ordibenzothiophenyl. The degree of substitution here may vary frommonosubstitution up to the maximum number of possible substituents.

Preferred compounds of the formula I for use in accordance with theinvention are notable in that at least two of the R¹, R² and R³ radicalsare para-OR and/or -NR₂ substituents. The at least two radicals here maybe only OR radicals, only NR₂ radicals, or at least one OR and at leastone NR₂ radical.

Particularly preferred compounds of the formula I for use in accordancewith the invention are notable in that at least four of the R¹, R² andR³ radicals are para-OR and/or -NR₂ substituents. The at least fourradicals here may be only OR radicals, only NR₂ radicals or a mixture ofOR and NR₂ radicals.

Very particularly preferred compounds of the formula I for use inaccordance with the invention are notable in that all of the R¹, R² andR³ radicals are para-OR and/or -NR₂ substituents. They may be only ORradicals, only NR₂ radicals or a mixture of OR and NR₂ radicals.

In all cases, the two R in the NR₂ radicals may be different from oneanother, but they are preferably the same.

Preferred divalent organic A¹, A² and A³ units are selected from thegroup consisting of (CH₂)_(m), C(R⁷)(R⁸), N(R⁹),

in which

-   m is an integer from 1 to 18,-   R⁴, R⁹ are each alkyl, aryl or a monovalent organic radical which    may comprise one, two or three optionally substituted aromatic or    heteroaromatic groups, where, in the case of two or three aromatic    or heteroaromatic groups, two of these groups in each case are    joined to one another by a chemical bond and/or via a divalent alkyl    radical,-   R⁵, R⁶, R⁷, R⁸ are each independently hydrogen atoms or radicals as    defined for R⁴ and R⁹,    and the aromatic and heteroaromatic rings of the units shown may    have further substitution.

The degree of substitution of the aromatic and heteroaromatic rings heremay vary from monosubstitution up to the maximum number of possiblesubstituents.

Preferred substituents in the case of further substitution of thearomatic and heteroaromatic rings include the substituents alreadymentioned above for the one, two or three optionally substitutedaromatic or heteroaromatic groups.

The compounds for use in accordance with the invention can be preparedby customary methods of organic synthesis known to those skilled in theart. References to relevant (patent) literature references canadditionally be found in the synthesis examples adduced below.

For the construction of a DSC, the n-semiconductive metal oxide used maybe a single metal oxide or a mixture of different oxides. Use of mixedoxides is also possible. The n-semiconductive metal oxide can especiallybe used as a nanoparticulate oxide, nanoparticles in this connectionbeing understood to mean particles which have an average particle sizeof less than 0.1 micrometer.

A nanoparticulate oxide is typically applied by a sintering process as athin porous film with high surface area to a conductive substrate (i.e.a carrier with a conductive layer as the first electrode).

Suitable substrates (also referred to hereinafter as carriers) are, aswell as metal foils, in particular polymer plates or films andespecially glass plates. Suitable electrode materials, especially forthe first electrode according to the above-described preferredstructure, are especially conductive materials, for example transparentconducting oxides (TCOs), for example fluorine- and/or indium-doped tinoxide (FTO and ITO) and/or aluminum-doped zinc oxide (AZO), carbonnanotubes or metal films. Alternatively or additionally, however, itwould also be possible to use thin metal films which still havesufficient transparency. The substrate can be covered or coated withthese conductive materials.

Since only a single substrate is generally required in thisconstruction, the construction of flexible cells is also possible. Thisenables a multitude of end uses which would be realizable with rigidsubstrates only with difficulty, if at all, for example use in bankcards, items of clothing, etc.

The first electrode, especially the TCO layer, may additionally becovered or coated with a solid buffer layer (for example of thickness 10to 200 nm), especially a metal oxide buffer layer, in order to preventdirect contact of the p-semiconductor with the TCO layer (see Peng etal., Coord. Chem. Rev. 248, 1479 (2004)). The buffer metal oxide whichcan be used in the buffer layer may, for example, comprise one or moreof the following materials: vanadium oxide; a zinc oxide; a tin oxide; atitanium oxide.

Thin layers or films of metal oxides are typically inexpensive solidsemiconductor materials (n-semiconductors), but their absorption, owingto large band gaps, is usually not in the visible region of the solarspectrum, but predominantly in the ultraviolet spectral range. For usein solar cells, the metal oxides therefore generally, as is the case forthe DSCs, have to be combined with a dye as a photosensitizer, whichabsorbs in the wavelength range of sunlight, i.e. at 300 to 2000 nm, andinjects electrons into the charge band of the semiconductor in theelectronically excited state. With the aid of a solid p-semiconductorused additionally in the cell, which is in turn reduced at thecounterelectrode, electrons can be recycled to the sensitizer, such thatit is regenerated.

Of particular interest for use in solar cells are the semiconductorszinc oxide, tin dioxide, titanium dioxide or mixtures of these metaloxides. The metal oxides can be used in the form of nanocrystallineporous layers. These layers have a large surface area which is coatedwith the sensitizer, such that a high absorption of sunlight isachieved. Metal oxide layers which are structured, for example nanorods,offer advantages such as higher electron mobilities or improved porefilling by the dye and the p-semiconductor.

The metal oxide semiconductors can be used alone or in the form ofmixtures. It is also possible to coat a metal oxide with one or moreother metal oxides. In addition, the metal oxides may also be applied asa coating on another semiconductor, for example GaP, ZnP or ZnS.

Particularly preferred semiconductors are zinc oxide and titaniumdioxide in the anatase modification, which is preferably used innanocrystalline form.

Moreover, the sensitizers can be combined advantageously with alln-semiconductors which typically find use in these solar cells.Preferred examples include metal oxides used in ceramics, such astitanium dioxide, zinc oxide, tin (IV) oxide, tungsten(VI) oxide,tantalum(V) oxide, niobium(V) oxide, cesium oxide, strontium titanate,zinc stannate, complex oxides of the perovskite type, for example bariumtitanate, and binary and ternary iron oxides, which may also be presentin nanocrystalline or amorphous form.

Owing to the strong absorption that customary organic dyes andphthalocyanines and porphyrins have, even thin layers or films of thedye-sensitized n-semiconductive metal oxide are sufficient to achievesufficient light absorption. Thin metal oxide films in turn have theadvantage that the probability of undesired recombination processesfalls and that the internal resistance of the dye subcell is reduced.For the n-semiconductive metal oxide, it is possible with preference touse layer thicknesses of 100 nm up to 20 micrometers, more preferably inthe range between 500 nm and approx. 5 micrometers.

Numerous dyes which are usable in the context of the present inventionare known from the prior art, such that reference may also be made tothe above description of the prior art regarding dye solar cells forpossible material examples. All dyes listed and claimed may in principlealso be present as pigments. Dye-sensitized solar cells based ontitanium dioxide as a semiconductor material are described, for example,in U.S. Pat. No. 4,927,721, Nature 353, p. 737-740 (1991) and U.S. Pat.No. 5,350,644, and also Nature 395, p. 583-585 (1998) and EP-A-1 176646. The dyes described in these documents can in principle also be usedadvantageously in the context of the present invention. These dye solarcells comprise monomolecular films of transition metal complexes,especially ruthenium complexes, which are bound to the titanium dioxidelayer via acid groups, as sensitizers.

Not least for reasons of cost, metal-free organic dyes have also beenproposed repeatedly as sensitizers, and are also usable in the contextof the present invention. High efficiencies of more than 4%, especiallyin solid-state dye solar cells, can be achieved, for example, withindoline dyes (see, for example, Schmidt-Mende et al., Adv. Mater. 2005,17, 813). U.S. Pat. No. 6,359,211 describes the use, which is alsousable in the context of the present invention, of cyanine, oxazine,thiazine and acridine dyes which have carboxyl groups bonded via analkylene radical for fixing to the titanium dioxide semiconductor.

JP-A-10-189065, 2000-243463, 2001-093589, 2000-100484 and 10-334954describe various perylene-3,4:9,10-tetracarboxylic acid derivativesunsubstituted in the perylene skeleton for use in semiconductor solarcells. These are specifically: perylenecarboximides which bearcarboxyalkyl, carboxyaryl, carboxyarylalkyl or carboxyalkylaryl radicalson the imide nitrogen atoms, and/or are imidated with p-diaminobenzenederivatives, in which the nitrogen atom of the amino group isp-substituted by two further phenyl radicals or is part of aheteroaromatic tricyclic system; perylene-3,4:9,10-tetracarboxylicmonoanhydride monoimides which bear the aforementioned radicals or alkylor aryl radicals without further functionalization on the imide nitrogenatom, or semicondensates of perylene-3,4:9,10-tetracarboxylicdianhydride with 1,2-diaminobenzenes or 1,8-diaminonaphthalenes, whichare converted by further reaction with primary amine to thecorresponding diimides or double condensates; condensates ofperylene-3,4:9,10-tetracarboxylic dianhydride with 1,2-diaminobenzenes,which are functionalized by carboxyl or amino radicals; andperylene-3,4:9,10-tetracarboximides which are imidated with aliphatic oraromatic diamines.

In New J. Chem. 26, p. 1155-1160 (2002), the sensitization of titaniumdioxide with perylene derivatives unsubstituted in the perylene skeleton(bay positions) is studied. Specific examples mentioned are9-dialkylaminoperylene-3,4-dicarboxylic anhydrides,perylene-3,4-dicarboximides which are 9-dialkylamino- or-carboxymethylamino-substituted and bear, on the imide nitrogen atom, acarboxymethyl or a 2,5-di(tert-butyl)phenyl radical, andN-dodecylaminoperylene-3,4:9,10-tetracarboxylic monoanhydride monoimide.However, the liquid electrolyte solar cells based on these perylenederivatives exhibited significantly lower efficiencies than a solar cellsensitized with a ruthenium complex for comparison.

Particularly preferred sensitizer dyes in the dye solar cell proposedare the perylene derivatives, terrylene derivatives and quaterrylenederivatives described in DE 10 2005 053 995 A1 or WO 2007/054470 A1. Theuse of these dyes leads to photovoltaic elements with high efficienciesand simultaneously high stabilities.

The rylenes exhibit strong absorption in the wavelength range ofsunlight and may, depending on the length of the conjugated system,cover a range from about 400 nm (perylene derivatives I from DE 10 2005053 995 A1) up to about 900 nm (quaterrylene derivatives I from DE 102005 053 995 A1). Rylene derivatives I based on terrylene absorb,according to their composition, in the solid state adsorbed on titaniumdioxide, within a range from about 400 to 800 nm. In order to achievemaximum utilization of the incident sunlight from the visible up to thenear infrared range, it is advantageous to use mixtures of differentrylene derivatives I. Occasionally, it may also be advisable to usedifferent rylene homologs.

The rylene derivatives I can be fixed easily and in a durable manner onthe metal oxide film. The binding is effected via the anhydride function(×1) or the carboxyl groups —COOH or —COO— formed in situ, or via theacid groups A present in the imide or condensate radicals ((×2) or(×3)). The rylene derivatives I described in DE 10 2005 053 995 A1 arevery suitable for use in dye-sensitized solar cells in the context ofthe present invention.

The dyes more preferably have an anchor group at one end of themolecule, which ensures their fixing on the n-semiconductor film. At theother end of the molecule, the dyes preferably comprise electron donorswhich facilitate the regeneration of the dye after the electron releaseto the n-semiconductor, and also prevent recombination with electronsalready released to the semiconductor.

For further details regarding the possible selection of a suitable dye,reference may be made, for example, again to DE 10 2005 053 995 A1. Forthe solid state dye solar cells described in the present document,especially ruthenium complexes, porphyrins, other organic sensitizersand preferably rylenes can be used.

The dyes can be fixed on the metal oxide films in a simple manner. Forexample, the n-semiconductive metal oxide films in the freshly sintered(still warm) state can be contacted with a solution or suspension of thedye in a suitable organic solvent over a sufficient period (e.g. about0.5 to 24 h). This can be done, for example, by immersing the substratecoated with the metal oxide into the solution of the dye.

If combinations of different dyes are to be used, they can be appliedsuccessively, for example, from one or more solutions or suspensionswhich comprise one or more of the dyes. It is also possible to use twodyes which are separated by a layer of, for example, CuSCN (on thissubject, see, for example, Tennakone, K. J., Phys. Chem. B. 2003, 107,13758). The most appropriate method can be determined comparativelyeasily in the individual case.

In principle, the dye may be present as a separate element or may beapplied in a separate step and applied separately to the remaininglayers. Alternatively or additionally, the dye may, however, also becombined or applied together with one or more of the other elements, forexample with the solid p-semiconductor. For example, adye-p-semiconductor combination which comprises an absorbent dye withp-semiconductive properties or, for example, a pigment with absorbentand p-semiconductive properties can be used.

In order to prevent recombination of the electrons in then-semiconductive metal oxide with the solid p-conductor, a kind ofpassivating layer which comprises a passivation material can be used.This layer should be as thin as possible and should as far as possiblecover only the sites on the n-semiconductive metal oxide which are asyet uncovered. Under some circumstances, the passivation material mayalso be applied to the metal oxide before the dye. Preferred passivationmaterials are especially the following substances: Al₂O₃; an aluminumsalt; silanes, for example CH₃SiCl₃; an organometallic complex,especially an Al³⁺ complex; Al³⁺, especially an Al³⁺ complex;4-tert-butylpyridine (TBP); MgO; 4-guanidinobutanoic acid (GBA); analkanoic acid; hexadecylmalonic acid (HDMA).

As already mentioned above, solid p-semiconductors are used in the solidstate dye solar cell. Solid p-semiconductors can also be used in theinventive dye-sensitized solar cells without any great increase in thecell resistance, especially when the dyes have strong absorption andtherefore require only thin n-semiconductor layers. More particularly,the p-semiconductor should essentially have a continuous, imperviouslayer in order that undesired recombination reactions which could arisefrom contact between the n-semiconductive metal oxide (especially innanoporous form) with the second electrode or the second half-cell arereduced.

A significant parameter influencing the selection of the p-semiconductoris the hole mobility, since this partly determines the hole diffusionlength (cf. Kumara, G., Langmuir, 2002, 18, 10493-10495). A comparisonof charge carrier mobilities in various Spiro compounds can be found,for example, in Saragi, T., Adv. Funct. Mater. 2006, 16, 966-974.

In addition, reference is made to the remarks regarding thep-semiconductive materials in the description of the prior art.

With regard to the remaining possible construction elements and thepossible construction of the dye solar cell, reference is likewise madeto the description above.

EXAMPLES Synthesis of the Compounds of the Formula I for Use inAccordance with the Invention A) Syntheses:

Synthesis route I:

Synthesis Step I-R1:

The synthesis in synthesis step I-R1 was effected based on theliterature references cited below:

-   a) Liu, Yunqi; Ma, Hong; Jen, Alex K-Y.; CHCOFS; Chem. Commun.; 24;    1998; 2747-2748,-   b) Goodson, Felix E.; Hauck, Sheila; Hartwig, John F.; J. Am. Chem.    Soc.; 121; 33; 1999; 7527-7539,-   c) Shen, Jiun Yi; Lee, Chung Ying; Huang, Tai-Hsiang; Lin, Jiann T.;    Tao, Yu-Tai; Chien, Chin-Hsiung; Tsai, Chiitang; J. Mater. Chem.;    15; 25; 2005; 2455-2463,-   d) Huang, Ping-Hsin; Shen, Jiun-Yi; Pu, Shin-Chien; Wen, Yuh-Sheng;    Lin, Jiann T.; Chou, Pi-Tai; Yeh, Ming-Chang P.; J. Mater. Chem.;    16; 9; 2006; 850-857,-   e) Hirata, Narukuni; Kroeze, Jessica E.; Park, Taiho; Jones, David;    Haque, Saif A.; Holmes, Andrew B.; Durrant, James R.; Chem. Commun.;    5; 2006; 535-537.

Synthesis Step I-R2:

The synthesis in synthesis step I-R2 was effected based on theliterature references cited below:

-   a) Huang, Qinglan; Evmenenko, Guennadi; Dutta, Pulak; Marks, Tobin    J.; J. Am. Chem. Soc.; 125; 48; 2003; 14704-14705,-   b) Bacher, Erwin; Bayerl, Michael; Rudati, Paula; Reckefuss, Nina;    Mueller, C. David; Meerholz, Klaus; Nuyken, Oskar; Macromolecules;    EN; 38; 5; 2005; 1640-1647,-   c) Li, Zhong Hui; Wong, Man Shing; Tao, Ye; D'Iorio, Marie; J. Org.    Chem.; EN; 69; 3; 2004; 921-927.

Synthesis Step I-R3:

The synthesis in synthesis step I-R3 was effected based on theliterature reference cited below:

-   J. Grazulevicius; J. of Photochem. and Photobio., A: Chemistry 2004    162(2-3), 249-252.

The compounds of the formula I can be prepared via the sequence of thesynthesis steps of synthesis route I shown above. The reactants can becoupled, for example, by Ullmann reaction with copper as a catalyst orwith palladium catalysis.

Synthesis route II:

Synthesis Step II-R1:

The synthesis in synthesis step II-R1 was effected based on theliterature references cited under II-R2.

Synthesis Step II-R2:

The synthesis in synthesis step II-R2 was effected based on theliterature references cited below:

-   a) Bacher, Erwin; Bayerl, Michael; Rudati, Paula; Reckefuss, Nina;    Müller, C. David; Meerholz, Klaus; Nuyken, Oskar; Macromolecules;    38; 5; 2005; 1640-1647,-   b) Goodson, Felix E.; Hauck, Sheila; Hartwig, John F.; J. Am. Chem.    Soc.; 121; 33; 1999; 7527-7539; Hauck, Sheila I.; Lakshmi, K. V.;    Hartwig, John F.; Org. Lett.; 1; 13; 1999; 2057-2060.

Synthesis Step II-R3:

The compounds of the formula I can be prepared via the sequence of thesynthesis steps of synthesis route II shown above. The reactants can becoupled, as also in synthesis route I, for example, by Ullmann reactionwith copper as a catalyst or with palladium catalysis.

Preparation of the Starting Amines:

When the diarylamines in synthesis steps I-R2 and II-R1 of synthesisroutes I and II are not commercially available, they can be prepared,for example, by Ullmann reaction with copper as a catalyst or underpalladium catalysis, according to the following reaction:

The synthesis was effected based on the review articles listed below:

Palladium-catalyzed C—N coupling reactions:

-   a) Yang, Buchwald; J. Organomet. Chem. 1999, 576 (1-2), 125-146,-   b) Wolfe, Marcoux, Buchwald; Acc. Chem. Res. 1998, 31, 805-818,-   c) Hartwig; Angew. Chem. Int. Ed. Engl. 1998, 37, 2046-2067.

Copper-catalyzed C—N coupling reactions:

-   a) Goodbrand, Hu; Org. Chem. 1999, 64, 670-674,-   b) Lindley; Tetrahedron 1984, 40, 1433-1456.

Example 1 Synthesis of the Compound ID367 Synthesis Route I SynthesisStep I-R1:

A mixture of 4,4′-dibromobiphenyl (93.6 g; 300 mmol), 4-methoxyaniline(133 g; 1.08 mol), Pd(dppf)Cl₂(Pd(1,1′-bis(diphenylphosphino)ferrocene)Cl₂; 21.93 g; 30 mmol) andt-BuONa (sodium tert-butoxide; 109.06 g; 1.136 mol) in toluene (1500 ml)was stirred under a nitrogen atmosphere at 110° C. for 24 hours. Aftercooling, the mixture was diluted with diethyl ether and filtered througha Celite® pad (from Carl Roth). The filter bed was washed with 1500 mleach of ethyl acetate, methanol and methylene chloride. The product wasobtained as a light brown solid (36 g; yield: 30%).

¹HNMR (400 MHz, DMSO): δ 7.81 (s, 2H), 7.34-7.32 (m, 4H), 6.99-6.97 (m,4H), 6.90-6.88 (m, 4H), 6.81-6.79 (m, 4H), 3.64 (s, 6H).

Synthesis Step I-R2:

Nitrogen was passed for a period of 10 minutes through a solution ofdppf (1,1′-bis(diphenylphosphino)ferrocene; 0.19 g; 0.34 mmol) andPd₂(dba)₃(tris(dibenzylideneacetone)dipalladium(0); 0.15 g; 0.17 mmol)in toluene (220 ml). Subsequently, t-BuONa (2.8 g; 29 mmol) was addedand the reaction mixture was stirred for a further 15 minutes.4,4′-Dibromobiphenyl (25 g; 80 mmol) and 4,4′-dimethoxydiphenylamine(5.52 g; 20 mmol) were then added successively. The reaction mixture washeated at a temperature of 100° C. under a nitrogen atmosphere for 7hours. After cooling to room temperature, the reaction mixture wasquenched with ice-water, and the precipitated solid was filtered off anddissolved in ethyl acetate. The organic layer was washed with water,dried over sodium sulfate and purified by column chromatography (eluent:5% ethyl acetate/hexane). A pale yellow-colored solid was obtained (7.58g, yield: 82%).

¹HNMR (300 MHz, DMSO-d₆): 7.60-7.49 (m, 6H), 7.07-7.04 (m, 4H),6.94-6.91 (m, 4H), 6.83-6.80 (d, 2H), 3.75 (s, 6H).

Synthesis Step I-R3:

N⁴,N^(4′)-Bis(4-methoxyphenyl)biphenyl-4,4′-diamine (product fromsynthesis step I-R1; 0.4 g; 1.0 mmol) and product from synthesis stepI-R2 (1.0 g; 2.2 mmol) were added under a nitrogen atmosphere to asolution of t-BuONa (0.32 g; 3.3 mmol) in o-xylene (25 ml).Subsequently, palladium acetate (0.03 g; 0.14 mmol) and a solution of10% by weight of P(t-Bu)₃ (tris-t-butylphosphine) in hexane (0.3 ml; 0.1mmol) were added to the reaction mixture which was stirred at 125° C.for 7 hours. Thereafter, the reaction mixture was diluted with 150 ml oftoluene and filtered through Celite®, and the organic layer was driedover Na₂SO₄. The solvent was removed and the crude product wasreprecipitated three times from a mixture of tetrahydrofuran(THF)/methanol. The solid was purified by column chromatography (eluent:20% ethyl acetate/hexane), followed by a precipitation with THF/methanoland an activated carbon purification. After removing the solvent, theproduct was obtained as a pale yellow solid (1.0 g, yield: 86%).

¹HNMR (400 MHz, DMSO-d₆): 7.52-7.40 (m, 8H), 6.88-7.10 (m, 32H),6.79-6.81 (d, 4H), 3.75 (s, 6H), 3.73 (s, 12H).

Example 2 Synthesis of the Compound ID447 Synthesis Route II SynthesisStep I-R1:

p-Anisidine (5.7 g, 46.1 mmol), t-BuONa (5.5 g, 57.7 mmol) and P(t-Bu)₃(0.62 ml, 0.31 mmol) were added to a solution of the product fromsynthesis step I-R2 (17.7 g, 38.4 mmol) in toluene (150 ml). Afternitrogen had been passed through the reaction mixture for 20 minutes,Pd₂(dba)₃ (0.35 g, 0.38 mmol) was added. The resulting reaction mixturewas left to stir under a nitrogen atmosphere at room temperature for 16hours. Subsequently, it was diluted with ethyl acetate and filteredthrough Celite®. The filtrate was washed twice with 150 ml each of waterand saturated sodium chloride solution. After the organic phase had beendried over Na₂SO₄ and the solvent had been removed, a black solid wasobtained. This solid was purified by column chromatography (eluent:0-25% ethyl acetate/hexane). This afforded an orange solid (14 g, yield:75%).

¹HNMR (300 MHz, DMSO): 7.91 (s, 1H), 7.43-7.40 (d, 4H), 7.08-6.81 (m,16H), 3.74 (s, 6H), 3.72 (s, 3H).

Synthesis Step I-R3:

t-BuONa (686 mg; 7.14 mmol) was heated at 100° C. under reducedpressure, then the reaction flask was purged with nitrogen and allowedto cool to room temperature. 2,7-Dibromo-9,9-dimethylfluorene (420 mg;1.19 mmol), toluene (40 ml) and Pd[P(^(t)Bu)₃]₂ (20 mg; 0.0714 mmol)were then added, and the reaction mixture was stirred at roomtemperature for 15 minutes. Subsequently,N,N,N′-p-trimethoxytriphenylbenzidine (1.5 g; 1.27 mmol) was added tothe reaction mixture which was stirred at 120° C. for 5 hours. Themixture was filtered through a Celite®/MgSO₄ mixture and washed withtoluene. The crude product was purified twice by column chromatography(eluent: 30% ethyl acetate/hexane) and, after twice reprecipitating fromTHF/methanol, a pale yellow-colored solid was obtained (200 mg, yield:13%).

¹H NMR: (400 MHz, DMSO-d₆): 7.60-7.37 (m, 8H), 7.02-6.99 (m, 16H),6.92-6.87 (m, 20H), 6.80-6.77 (d, 2H), 3.73 (s, 6H), 3.71 (s, 12H), 1.25(s, 6H)

Example 3 Synthesis of the Compound ID453 Synthesis Route I a)Preparation of the Starting Amine: Step 1:

NaOH (78 g; 4 eq) was added to a mixture of 2-bromo-9H-fluorene (120 g;1 eq) and BnEt₃NCl (benzyltriethylammonium chloride; 5.9 g; 0.06 eq) in580 ml of DMSO (dimethyl sulfoxide). The mixture was cooled withice-water, and methyl iodide (MeI) (160 g; 2.3 eq) was slowly addeddropwise. The reaction mixture was left to stir overnight, then pouredinto water and subsequently extracted three times with ethyl acetate.The combined organic phases were washed with a saturated sodium chloridesolution and dried over Na2SO4, and the solvent was removed. The crudeproduct was purified by column chromatography using silica gel (eluent:petroleum ether). After washing with methanol, the product(2-bromo-9,9′-dimethyl-9H-fluorene) was obtained as a white solid (102g).

¹HNMR (400 MHz, CDCl3): δ 1.46 (s, 6H), 7.32 (m, 2H), 7.43 (m, 2H), 7.55(m, 2H), 7.68 (m, 1H)

Step 2:

p-Anisidine (1.23 g; 10.0 mmol) and 2-bromo-9,9′-dimethyl-9H-fluorene(3.0 g; 11.0 mmol) were added under a nitrogen atmosphere to a solutionof t-BuONa (1.44 g; 15.0 mmol) in 15 ml of toluene. Pd₂(dba)₃ (92 mg;0.1 mmol) and a 10% by weight solution of P(t-Bu)₃ in hexane (0.24 ml;0.08 mmol) were added, and the reaction mixture was stirred at roomtemperature for 5 hours. Subsequently, the mixture was quenched withice-water, and the precipitated solid was filtered off and dissolved inethyl acetate. The organic phase was washed with water and dried overNa₂SO₄. After purifying the crude product by column chromatography(eluent: 10% ethyl acetate/hexane), a pale yellow-colored solid wasobtained (1.5 g, yield: 48%).

¹HNMR (300 MHz, C₆D₆): 7.59-7.55 (d, 1H), 7.53-7.50 (d, 1H), 7.27-7.22(t, 2H), 7.19 (s, 1H), 6.99-6.95 (d, 2H), 6.84-6.77 (m, 4H), 4.99 (s,1H), 3.35 (s, 3H), 1.37 (s, 6H).

b) Preparation of the Compound for Use in Accordance with the Invention

Synthesis Step I-R2:

Product from a) (4.70 g; 10.0 mmol) and 4,4′-dibromobiphenyl (7.8 g; 25mmol) were added to a solution of t-BuONa (1.15 g; 12 mmol) in 50 ml oftoluene under nitrogen. Pd₂(dba)₃ (0.64 g; 0.7 mmol) and DPPF (0.78 g;1.4 mmol) were added, and the reaction mixture was left to stir at 100°C. for 7 hours. After the reaction mixture had been quenched withice-water, the precipitated solid was filtered off and it was dissolvedin ethyl acetate. The organic phase was washed with water and dried overNa₂SO₄. After purifying the crude product by column chromatography(eluent: 1% ethyl acetate/hexane), a pale yellow-colored solid wasobtained (4.5 g, yield: 82%).

¹1HNMR (400 MHz, DMSO-d6): 7.70-7.72 (d, 2H), 7.54-7.58 (m, 6H),7.47-7.48 (d, 1H), 7.21-7.32 (m, 3H), 7.09-7.12 (m, 2H), 6.94-6.99 (m,4H), 3.76 (s, 3H), 1.36 (s, 6H).

Synthesis Step I-R3:

N⁴,N^(4′)-Bis(4-methoxyphenyl)biphenyl-4,4′-diamine (0.60 g; 1.5 mmol)and product from the preceding synthesis step I-R2 (1.89 g; 3.5 mmol)were added under nitrogen to a solution of t-BuONa (0.48 g; 5.0 mmol) in30 ml of o-xylene. Palladium acetate (0.04 g; 0.18 mmol) and P(t-Bu)₃ ina 10% by weight solution in hexane (0.62 ml; 0.21 mmol) were added, andthe reaction mixture was stirred at 125° C. for 6 hours. Subsequently,the mixture was diluted with 100 ml of toluene and filtered throughCelite®. The organic phase was dried over Na₂SO₄ and the resulting solidwas purified by column chromatography (eluent: 10% ethylacetate/hexane). This was followed by reprecipitation from THF/methanolto obtain a pale yellow-colored solid (1.6 g, yield: 80%).

¹HNMR (400 MHz, DMSO-d₆): 7.67-7.70 (d, 4H), 7.46-7.53 (m, 14H),7.21-7.31 (m, 4H), 7.17-7.18 (d, 2H), 7.06-7.11 (m, 8H), 6.91-7.01 (m,22H), 3.75 (s, 12H), 1.35 (s, 12H).

Further compounds of the formula I for use in accordance with theinvention:

The compounds listed below were obtained analogously to the synthesesdescribed above:

Example 4 Compound ID320

¹HNMR (300 MHz, THF-d₈): δ 7.43-7.46 (d, 4H), 7.18-7.23 (t, 4H),7.00-7.08 (m, 16H), 6.81-6.96 (m, 18H), 3.74 (s, 12H)

Example 5 Compound ID321

¹HNMR (300 MHz, THF-d₈): δ 7.37-7.50 (t, 8H), 7.37-7.40 (d, 4H),7.21-7.26 (d, 4H), 6.96-7.12 (m, 22H), 6.90-6.93 (d, 4H), 6.81-6.84 (d,8H), 3.74 (s, 12H)

Example 6 Compound ID366

¹HNMR (400 MHz, DMSO-d6): δ 7.60-7.70 (t, 4H), 7.40-7.55 (d, 2H),7.17-7.29 (m, 8H), 7.07-7.09 (t, 4H), 7.06 (s, 2H), 6.86-7.00 (m, 24H),3.73 (s, 6H), 1.31 (s, 12H)

Example 7 Compound ID368

¹HNMR (400 MHz, DMSO-d6): δ 7.48-7.55 (m, 8H), 7.42-7.46 (d, 4H),7.33-7.28 (d, 4H), 6.98-7.06 (m, 20H), 6.88-6.94 (m, 8H), 6.78-6.84 (d,4H), 3.73 (s, 12H), 1.27 (s, 18H)

Example 8 Compound ID369

¹HNMR (400 MHz, THF-d8): δ 7.60-7.70 (t, 4H), 7.57-7.54 (d, 4H),7.48-7.51 (d, 4H), 7.39-7.44 (t, 6H), 7.32-7.33 (d, 2H), 7.14-7.27 (m,12H), 7.00-7.10 (m, 10H), 6.90-6.96 (m, 4H), 6.80-6.87 (m, 8H), 3.75 (s,12H), 1.42 (s, 12H)

Example 9 Compound ID446

¹HNMR (400 MHz, dmso-d₆): δ 7.39-7.44 (m, 8H), 7.00-7.07 (m, 13H),6.89-6.94 (m, 19H), 6.79-6.81 (d, 4H), 3.73 (s, 18H)

Example 10 Compound ID450

¹HNMR (400 MHz, dmso-d₆): δ 7.55-7.57 (d, 2H), 7.39-7.45 (m, 8H),6.99-7.04 (m, 15H), 6.85-6.93 (m, 19H), 6.78-6.80 (d, 4H), 3.72 (s,18H), 1.68-1.71 (m, 6H), 1.07 (m, 6H), 0.98-0.99 (m, 8H), 0.58 (m, 6H)

Example 11 Compound ID452

¹HNMR (400 MHz, DMSO-d6): δ 7.38-7.44 (m, 8H), 7.16-7.19 (d, 4H),6.99-7.03 (m, 12H), 6.85-6.92 (m, 20H), 6.77-6.79 (d, 4H), 3.74 (s,18H), 2.00-2.25 (m, 4H), 1.25-1.50 (m, 6H)

Example 12 Compound ID480

¹HNMR (400 MHz, DMSO-d6): δ 7.40-7.42 (d, 4H), 7.02-7.05 (d, 4H),6.96-6.99 (m, 28H), 6.74-6.77 (d, 4H), 3.73 (s, 6H), 3.71 (s, 12H)

Example 13 Compound ID518

¹HNMR (400 MHz, DMSO-d6): 7.46-7.51 (m, 8H), 7.10-7.12 (d, 2H),7.05-7.08 (d, 4H), 6.97-7.00 (d, 8H), 6.86-6.95 (m, 20H), 6.69-6.72 (m,2H), 3.74 (s, 6H), 3.72 (s, 12H), 1.24 (t, 12H)

Example 14 Compound ID519

¹HNMR (400 MHz, DMSO-d6): 7.44-7.53 (m, 12H), 6.84-7.11 (m, 32H),6.74-6.77 (d, 2H), 3.76 (s, 6H), 3.74 (s, 6H), 2.17 (s, 6H), 2.13 (s,6H)

Example 15 Compound ID521

¹HNMR (400 MHz, THF-d₆): 7.36-7.42 (m, 12H), 6.99-7.07 (m, 20H),6.90-6.92 (d, 4H), 6.81-6.84 (m, 8H), 6.66-6.69 (d, 4H), 3.74 (s, 12H),3.36-3.38 (q, 8H), 1.41-1.17 (t, 12H)

Example 16 Compound ID522

¹HNMR (400 MHz, DMSO-d₆): 7.65 (s, 2H), 7.52-7.56 (t, 2H), 7.44-7.47 (t,1H), 7.37-7.39 (d, 2H), 7.20-7.22 (m, 10H), 7.05-7.08 (dd, 2H),6.86-6.94 (m, 8H), 6.79-6.80-6.86 (m, 12H), 6.68-6.73, (dd, 8H),6.60-6.62 (d, 4H), 3.68 (s, 12H), 3.62 (s, 6H)

Example 17 Compound ID523

¹HNMR (400 MHz, THF-d₈): 7.54-7.56 (d, 2H), 7.35-7.40 (dd, 8H), 7.18 (s,2H) 7.00-7.08 (m, 18H), 6.90-6.92 (d, 4H), 6.81-6.86 (m, 12H), 3.75 (s,6H), 3.74 (s, 12H), 3.69 (s, 2H)

Example 18 Compound ID565

¹HNMR (400 MHz, THF-d8): 7.97-8.00 (d, 2H), 7.86-7.89 (d, 2H), 7.73-7.76(d, 2H), 7.28-7.47 (m, 20H), 7.03-7.08 (m, 16H), 6.78-6.90 (m, 12H),3.93-3.99 (q, 4H), 3.77 (s, 6H), 1.32-1.36 (s, 6H)

Example 19 Compound ID568

¹HNMR (400 MHz, DMSO-d6): 7.41-7.51 (m, 12H), 6.78-7.06 (m, 36H),3.82-3.84 (d, 4H), 3.79 (s, 12H), 1.60-1.80 (m, 2H), 0.60-1.60 (m, 28H)

Example 20 Compound ID569

¹HNMR (400 MHz, DMSO-d6): 7.40-7.70 (m, 10H), 6.80-7.20 (m, 36H),3.92-3.93 (d, 4H), 2.81 (s, 12H), 0.60-1.90 (m, 56H)

Example 21 Compound ID572

¹HNMR (400 MHz, THF-d8): 7.39-7.47 (m, 12H), 7.03-7.11 (m, 20H),6.39-6.99 (m, 8H), 6.83-6.90 (m, 8H), 3.78 (s, 6H), 3.76 (s, 6H), 2.27(s, 6H)

Example 22 Compound ID573

¹HNMR (400 MHz, THF-d8): 7.43-7.51 (m, 20H), 7.05-7.12 (m, 24H),6.87-6.95 (m, 12H), 3.79 (s, 6H), 3.78 (s, 12H)

Example 23 Compound ID575

¹HNMR (400 MHz, DMSO-d6): 7.35-7.55 (m, 8H), 7.15-7.45 (m, 4H),6.85-7.10 (m, 26H), 6.75-6.85 (d, 4H), 6.50-6.60 (d, 2H), 3.76 (s, 6H),3.74 (s, 12H)

Example 24 Compound ID629

¹HNMR (400 MHz, THF-d₈): 7.50-7.56 (dd, 8H), 7.38-7.41 (dd, 4H),7.12-7.16 (d, 8H) 7.02-7.04 (dd, 8H), 6.91-6.93 (d, 4H), 6.82-6.84 (dd,8H), 6.65-6.68 (d, 4H) 3.87 (s, 6H), 3.74 (s, 12H)

Example 25 Compound ID631

¹HNMR (400 MHz, THF-d₆): 7.52 (d, 2H), 7.43-7.47 (dd, 2H), 7.34-7.38 (m,8H), 7.12-7.14 (d, 2H), 6.99-7.03 (m, 12H), 6.81-6.92 (m, 20H), 3.74 (s,18H), 2.10 (s, 6H)

For spiro-MeOTAD and the compounds of examples 1 to 23, the glasstransition temperature Tg (° C.) and the morphology M were determined ineach case by means of DSC, the decomposition temperature Td by means ofTGA (° C.), and the solubility L in chlorobenzene (mg/ml)—since this isone of the best known solvents for spiro-MeOTAD—at room temperature, andthe data are compared in table 1 below. In the “M” column, theabbreviations here mean:

-   a: amorphous; only one glass transition at Tg could be detected here    during the DSC measurement in the course of the first heating;-   a*: the amorphous state was additionally confirmed by X-ray    diffraction;-   sc: semi-crystalline; the first heating during the DSC measurement    resulted in crystallization after the glass transition at Tg;

TABLE 1 Example ID Tg M Td L Spiro- 120 sc 440 200-230 MeOTAD(comparative) 1 367 136  a* 450  700-1000 2 447 137 a 430  900-1800 3453 156 a 440 450-700 4 320 96  a* 450  760-1000 5 321 143  a* 460 900-1150 6 366 127  a* 460 >1100  7 368 154 a 460  500-1000 8 369 154 a460 300-450 9 446 120 a 430 1250-2500 10 450 105 a 420  900-1800 11 452123 a 450  650-1300 12 480 105 a 430 >280 13 518 150 a 430 400-800 14519 128 a 450 450-900 15 521 138 a 420 400-550 16 522 158 a 450 900-1400 17 523 141 a 450 1250-2500 18 565 143 a 450 >900 19 568 65 a360 >650 20 569 47 a 440 400-800 21 572 138 a 450 >900 22 573 148 a460 >1000  23 575 110 a 440 >400 24 629 134 a 430 >2000  25 631 134 a440 >1300 

It can be inferred from table 1 that the compounds for use in accordancewith the invention are all present in amorphous form. It can thereforebe expected that they have a significantly lower tendency to crystallizeand, with regard to a prolonged lifetime, bring about more advantageousproperties of the DSCs produced therewith than DSCs based on thecomparative compound spiro-MeOTAD. In addition, the compounds for use inaccordance with the invention possess significantly better solubilitythan the comparative compound spiro-MeOTAD, which has a positive effecton the degree of pore filling in the production of the DSCs.

Solubilities in Other Solvents:

Since chlorobenzene possesses low to moderate toxicity (LD50 of 2.9 g/kgaccording to Manfred Rossberg et al. “Chlorinated Hydrocarbons” inUllmann's Encyclopedia of Industrial Chemistry Wiley-VCH, Weinheim,2006) the compounds were also examined by way of example for theirsolubility in other solvents. As can be inferred from table 2, theyhave, in the predominant number of cases, increased solubility comparedto spiro-MeOTAD (all data in mg/ml). In other words, the application ofthe hole conductors for use in accordance with the invention in highconcentration is also possible from other solvents.

TABLE 2 Solvent (Example) Toluene Tetrahydrofuran Ethyl acetate AnisoleSpiro- 100 120-160 <6 65-75 MeO-TAD ID367 (1) 320-500 370-550 70-80 450-700 ID447 (2) >520  750-1500 >660 n.d. ID453 (3) 170-230 340-680 40n.d. ID320 (4) 280 >280 140 n.d. ID321 (5) >100 >240 15 n.d. ID366(6) >380 >440 >560 n.d. ID368 (7) >240 180-360 >380 n.d. ID369 (8)140-170 100-150 140-280  n.d. ID446 (9) >460 1000-2000 50-65  n.d. ID452(11) >270 300-600 n.d. n.d. ID518 (13) 160-240  550-1100 >400 n.d. ID519(14) 240-350 >500 >460 n.d. ID521 (15)  500-1000 440-580 90-110 n.d.ID522 (16) 490-980 400-600 600-1200 n.d. ID523 (17)  900-1800 400-550240-480  n.d. ID565 (18) 400-800 >850 <40 >1000 ID572 (21) >500 >80060-100  >400 ID573 (22)  500-1000 >580 <20  550-1100 ID629(24) >1500 >2000 >1300 >1500 ID631 (25)  500-1000 1000-2000 700-1400 500-1000 “n.d.” means not determined “>” in conjunction with anumerical value means that the solubility of the compound is greaterthan the numerical value reported.B) Test of the Compounds for Use in Accordance with the Invention inDSCs:

The structure of a DSC generally comprises the following layers:

-   -   138 top contact (cathode)    -   124 hole-conducting material    -   123 hole-conducting material (in pores of the 120/122 layer)    -   122 sensitizing dye    -   120 n-semiconductive metal oxide    -   119 optional buffer layer    -   116 front contact (anode)    -   114 carrier

On the carrier 114 there is a layer 116 of a transparent conductingoxide (TCO), for example FTO (fluorine-doped tin oxide) or ITO (indiumtin oxide). This TCO layer constitutes the front contact (anode).

An optional buffer layer 119 may be applied to the front contact, saidbuffer layer being intended to suppress or at least hinder the migrationof the holes to the front electrode 116. The buffer layer 119 used istypically a single layer of a (preferably non-nanoporous) titaniumdioxide and generally has a thickness between 10 nm and 500 nm. Suchlayers can be obtained, for example, by sputtering and/or spraypyrolysis.

The optional buffer layer 119 is followed by an about 1 μm- to 20μm-thick layer 120 of a porous n-semiconductive metal oxide which issensitized with a very thin, typically monomolecular layer 122 of a dye.The n-semiconductive metal oxide used is usually titanium dioxide, butother oxides are also conceivable.

The layer 120 of the n-semiconductive metal oxide sensitized with thedye (layer 122) is followed by a layer 123 of hole-conducting material.This material fills the pores of the layer 120/122 (metal oxide/dye)generally more or less completely, a maximum fill level being desirable.An interpenetrating layer/intimate permeation of hole-conductingmaterial and n-semiconductive metal oxide/dye thus arises. In addition,the hole-conducting material on the metal oxide/dye layer forms aprotruding layer 124 which is generally 10 nm to 500 nm thick, and oneof its functions is to prevent electrons from passing out of the metaloxide into the cathode 138.

A counterelectrode 138 is applied as a top contact (cathode) to thelayer 124.

In order to use the DSC, i.e. to be able to tap off a photovoltage anddraw a photocurrent, a front contact (anode) 116 and the top contact(cathode) 138 are provided with appropriate conductive contacts, which,however, were not drawn in here for reasons of clarity.

Dyes Used: D102:

Commercially available from Mitsubishi.

D205:

Synthesizable according to Seigo Ito et al., “High-conversion-efficiencyorganic dye-sensitized solar cells with a novel indoline dye”, Chem.Commun. 41, 5194-5196 (2008).

Perylene 1:

The synthesis was effected analogously to the synthesis of the compoundI7 from example 7 on page 80 of WO 2007/054470 A1.

Perylene 2:

One equivalent of perylene 1 was reacted with 8 equivalents of glycineand one equivalent of anhydrous zinc acetate in N-methylpyrrolidone at130° C. overnight. The product was purified using silica gel.

Perylene 3:

One equivalent of the compound I24 from example 24 on page 109 of WO2007/054470 A1 was reacted with 8 equivalents of glycine and oneequivalent of anhydrous zinc acetate in N-methylpyrrolidone at 130° C.overnight. The product was purified using silica gel.

The test DSCs were prepared as described below:

DSC 1:

The base material used was glass plates coated with fluorine-doped tinoxide (FTO) of dimensions 25 mm×15 mm×3 mm (Nippon Sheet Glass), whichwere treated successively with glass cleaner (RBS 35), demineralizedwater and acetone, in each case in an ultrasound bath for 5 minutes,then boiled in isopropanol for 10 minutes and dried in a nitrogenstream.

To produce the solid TiO₂ buffer layer 119, a spray pyrolysis method asdescribed in L. Kavan and M. Grätzel, Electrochim. Acta 40, 643 (1995)was used. Alternatively or additionally, it is, however, also possibleto use other processes, for example sputtering processes (see P. Frachet al., Thin Solid Films 445 (2003) 251-258; D. Glöβ et al., Suf. coat.Technol. 200 (2005) 967-971).

A layer of an n-semiconductive metal oxide 120 was applied to the bufferlayer 119. For this purpose, a TiO₂ paste (Dyesol, DSL 18NR-T) wasapplied by spinning with a spin coater at 4500 revolutions per minuteand dried at 90° C. for 30 minutes. After heating to 450° C. for 45minutes and sintering at 450° C. for 30 minutes, this resulted in a TiO₂layer thickness of approximately 1.8 μm.

The intermediates thus produced were then treated with TiCl₄, asdescribed by Grätzel, for example, in Grätzel M. et al., Adv. Mater.2006, 18, 1202.

After removal from the sintering oven, the sample was cooled to 80° C.and immersed into a 0.5 mM solution of the dye D102 in 1:1acetonitrile/t-BuOH for 12 hours. After removal from the solution, thesample was subsequently rinsed with the same solvent and dried in anitrogen stream.

Next, the p-semiconductor ID367 was applied. For this purpose, asolution of 130 mM ID367, 12 mM LiN(SO₂CF₃)₂ (Aldrich), 47 mM4-t-butylpyridine (Aldrich) in chlorobenzene was made up. 75 μl of thissolution were applied to the sample and allowed to act for 60 seconds.Thereafter, the supernatant solution was spun off at 2000 revolutionsper minute for 30 seconds and dried in ambient air for 3 hours.

The top contact (cathode) was applied by thermal metal evaporation underreduced pressure. For this purpose, the sample was provided with a maskin order to apply, by vapor deposition, 4 individual, separaterectangular top contacts with dimensions of in each case approx. 5 mm×4mm to the active region, each of them connected to a contact area ofabout 3 mm×2 mm in size. The metal used was Ag, which was evaporated ata rate of 0.1 nm/s at a pressure of 5·10⁻⁵ mbar, so as to form a layerof thickness about 200 nm.

To determine the efficiency η, the particular current/voltagecharacteristic was measured with a Source Meter Model 2400 (KeithleyInstruments Inc.) with irradiation with a xenon lamp (LOT-Oriel) as thesolar simulator.

Current/voltage characteristics were measured at an illuminationintensity of 10 mW/cm² (0.1 sun) and 100 mW/cm² (1 sun). The currentdensity at 0.1 sun was multiplied by the factor of 10 in order to obtainthe direct comparison to the measurement at 1 sun.

At 0.1 sun and 1 sun, the short-circuit current densities I_(SC) were1.01 mA/cm² and 9.76 mA/cm² respectively, the terminal voltages V_(OC)with an open circuit 0.78 V and 0.86 V respectively, the fill factors(FF) 68% and 53% respectively, and the efficiencies 5.3% and 4.4%respectively.

Comparative Example for DSC 1

As described in example DSC 1, a solid DSC was produced with the holeconductor spiro-MeO-TAD. For this purpose, a solution of 163 mMspiro-MeO-TAD, 15 mM LiN(SO₂CF₃)₂ (Aldrich), 60 mM 4-t-butylpyridine(Aldrich) in chlorobenzene was made up. At 0.1 sun and 1 sun, theshort-circuit current densities I_(SC) were 1.10 mA/cm² and 10.60 mA/cm²respectively, the terminal voltages V_(OC) with an open circuit 0.74 Vand 0.80 V respectively, the fill factors (FF) 69% and 47% respectively,and the efficiencies 5.6% and 4.0% respectively.

DSC 2:

As described in the example DSC 1, a solid DSC was produced with thehole conductor ID447 and the dye D102 (hole conductor solution: 167 mMID447, 15 mM LiN(SO₂CF₃)₂, 61 mM 4-t-butylpyridine in chlorobenzene).

At 0.1 sun and 1 sun, the short-circuit current densities I_(SC) were0.91 mA/cm² and 6.95 mA/cm² respectively, the terminal voltages V_(OC)with an open circuit 0.72 V and 0.78 V respectively, the fill factors(FF) 56% and 33% respectively, and the efficiencies 3.8% and 1.8%respectively.

DSC 3:

As described in the example DSC 1, a solid DSC was produced with thehole conductor ID453 and the dye D102 (hole conductor solution: 151 mMID453, 14 mM LiN(SO₂CF₃)₂, 55 mM 4-t-butylpyridine in chlorobenzene).

At 0.1 sun and 1 sun, the short-circuit current densities I_(SC) were0.87 mA/cm² and 7.75 mA/cm² respectively, the terminal voltages V_(OC)with an open circuit 0.84 V and 0.90 V respectively, the fill factors(FF) 61% and 34% respectively, and the efficiencies 4.5% and 2.3%respectively.

DSC 4:

As described in the example DSC 1, a solid DSC was produced with thehole conductor ID522 and the dye D102 (hole conductor solution: 161 mMID522, 15 mM LiN(SO₂CF₃)₂, 58 mM 4-t-butylpyridine in chlorobenzene).The thickness of the nanoporous TiO₂ layer this time was approx. 2.2 μminstead of approx. 1.8 μm.

At 0.1 sun and 1 sun, the short-circuit current densities I_(SC) were0.83 mA/cm² and 8.77 mA/cm² respectively, the terminal voltages V_(OC)with an open circuit 0.76 V and 0.84 V respectively, the fill factors(FF) 69% and 45% respectively, and the efficiencies 4.4% and 3.3%respectively.

Comparative Example for DSC 4

As described in the example DSC 4, a solid DSC was produced with thehole conductor spiro-MeO-TAD and the dye D102 (hole conductor solution:163 mM spiro-MeO-TAD, 15 mM LiN(SO₂CF₃)₂ (Aldrich), 60 mM4-t-butylpyridine (Aldrich) in chlorobenzene). The thickness of thenanoporous TiO₂ layer was approx. 2.2 μm as in the example DSC 4.

At 0.1 sun and 1 sun, the short-circuit current densities I_(SC) were0.92 mA/cm² and 9.10 mA/cm² respectively, the terminal voltages V_(OC)with an open circuit 0.74 V and 0.82 V respectively, the fill factors(FF) 69% and 50% respectively, and the efficiencies 4.7% and 3.7%respectively.

DSC 5:

As described in the example DSC 1, a solid DSC was produced with thehole conductor ID572 and the dye D102 (hole conductor solution: 178 mMID572, 16 mM LiN(SO₂CF₃)₂, 65 mM 4-t-butylpyridine in chlorobenzene).The thickness of the nanoporous TiO₂ layer was approx. 1.8 μm as inexample DSC 1.

At 0.1 sun and 1 sun, the short-circuit current densities I_(SC) were0.91 mA/cm² and 8.52 mA/cm² respectively, the terminal voltages V_(OC)with an open circuit 0.84 V and 0.92 V respectively, the fill factors(FF) 58% and 40% respectively, and the efficiencies 4.5% and 3.1%respectively.

DSC 6:

As described in the example DSC 1, a solid DSC was produced with thehole conductor ID367 and the dye D205 (hole conductor solution: 130 mMID367, 12 mM LiN(SO₂CF₃)₂, 47 mM 4-t-butylpyridine in chlorobenzene).Dye bath: 0.5 mM solution of the dye D205 (as described in Schmidt-Mendeet al., Adv. Mater. 2005, 17, 813) in 1:1 acetonitrile/t-BuOH.

At 0.1 sun and 1 sun, the short-circuit current densities I_(SC) were0.97 mA/cm² and 8.92 mA/cm² respectively, the terminal voltages V_(OC)with an open circuit 0.80 V and 0.88 V respectively, the fill factors(FF) 70% and 46% respectively, and the efficiencies 5.4% and 3.7%respectively.

Comparative Example for DSC6

As described in the example DSC6, a solid DSC was produced with the holeconductor spiro-MeO-TAD and the dye D205 (hole conductor solution: 123mM spiro-MeO-TAD, 11 mM LiN(SO₂CF₃)₂, 45 mM 4-t-butylpyridine inchlorobenzene).

At 0.1 sun and 1 sun, the short-circuit current densities I_(SC) were0.96 mA/cm² and 9.32 mA/cm² respectively, the terminal voltages V_(OC)with an open circuit 0.76 V and 0.86 V respectively, the fill factors(FF) 68% and 49% respectively, and the efficiencies 4.9% and 3.9%respectively.

DSC 7:

As described in the example DSC 6, a solid DSC was produced with thehole conductor ID518 and the dye D205 (hole conductor solution: 202 mMID518, 18 mM LiN(SO₂CF₃)₂, 74 mM 4-t-butylpyridine in chlorobenzene).The thickness of the nanoporous TiO₂ layer this time was 3.2 μm insteadof approx. 1.8 μm.

At 0.1 sun and 1 sun, the short-circuit current densities I_(SC) were0.81 mA/cm² and 8.57 mA/cm² respectively, the terminal voltages V_(OC)with an open circuit 0.74 V and 0.82 V respectively, the fill factors(FF) 63% and 33% respectively, and the efficiencies 3.8% and 2.3%respectively.

Comparative Example for DSC 7

As described in the example DSC 7, a solid DSC was produced with thehole conductor spiro-MeO-TAD and the dye D205 (hole conductor solution:204 mM spiro-MeO-TAD, 19 mM LiN(SO₂CF₃)₂, 74 mM 4-t-butylpyridine inchlorobenzene). The thickness of the nanoporous TiO₂ layer was, as inDSC 7, 3.2 μm instead of approx. 1.8 μm.

At 0.1 sun and 1 sun, the short-circuit current densities I_(SC) were0.95 mA/cm² and 10.0 mA/cm² respectively, the terminal voltages V_(OC)with an open circuit 0.72 V and 0.78 V respectively, the fill factors(FF) 68% and 37% respectively, and the efficiencies 4.7% and 2.9%respectively.

DSC 8:

As described in the example DSC 7, a solid DSC was produced with thehole conductor ID522 and the dye D205 (hole conductor solution: 201 mMID522, 18 mM LiN(SO₂CF₃)₂, 73 mM 4-t-butylpyridine in chlorobenzene).The thickness of the nanoporous TiO₂ layer was, as in DSC 7, 3.2 μminstead of approx. 1.8 μm.

At 0.1 sun and 1 sun, the short-circuit current densities I_(SC) were0.56 mA/cm² and 6.57 mA/cm² respectively, the terminal voltages V_(OC)with an open circuit 0.74 V and 0.84 V respectively, the fill factors(FF) 64% and 51% respectively, and the efficiencies 2.7% and 2.8%respectively.

DSC 9:

As described in the example DSC 7, a solid DSC was produced with thehole conductor ID523 and the dye D205 (hole conductor solution: 214 mMID523, 19 mM LiN(SO₂CF₃)₂, 78 mM 4-t-butylpyridine in chlorobenzene).The thickness of the nanoporous TiO₂ layer was, as in DSC 7, 3.2 μminstead of approx. 1.8 μm.

At 0.1 sun and 1 sun, the short-circuit current densities I_(SC) were0.95 mA/cm² and 6.76 mA/cm² respectively, the terminal voltages V_(OC)with an open circuit 0.74 V and 0.80 V respectively, the fill factors(FF) 58% and 34% respectively, and the efficiencies 4.1% and 1.8%respectively.

DSC 10:

As described in example DSC 1, a solid DSC was produced with the holeconductor ID367 and the dye perylene1 (dye bath: 0.5. mM solution of thedye perylene1 in dichloromethane). For this purpose, a solution of 130mM ID367, 12 mM LiN(SO₂CF₃)₂ (Aldrich), 47 mM 4-t-butylpyridine(Aldrich) in chlorobenzene was made up.

At 0.1 sun and 1 sun the short-circuit current densities I_(SC) were0.38 mA/cm² and 2.78 mA/cm² respectively, the terminal voltages V_(OC)with an open circuit 0.66 V and 0.74 V respectively, the fill factors(FF) 53% and 51% respectively, and the efficiencies 1.3% and 1.1%respectively.

Comparative Example DSC 10

As described in example DSC 10, a solid DSC was produced with the holeconductor spiro-MeO-TAD and the dye perylene 1 (dye bath: 0.5 mMsolution of the dye perylene 1 in dichloromethane). For this purpose, asolution of 123 mM spiro-MeO-TAD, 11 mM LiN(SO₂CF₃)₂ (Aldrich), 45 mM4-t-butylpyridine (Aldrich) in chlorobenzene was made up.

At 0.1 sun and 1 sun, the short-circuit current densities I_(SC) were0.37 mA/cm² and 2.58 mA/cm² respectively, the terminal voltages V_(OC)with an open circuit 0.60 V and 0.68 V respectively, the fill factors(FF) 55% and 54% respectively, and the efficiencies 1.2% and 0.9%respectively.

DSC 11:

As described in example, DSC 1, a solid DSC was produced with the holeconductor ID367 and the dye perylene 2 (dye bath: 0.5 mM solution of thedye perylene 2 in dichloromethane). For this purpose, a solution of 130mM ID367, 12 mM LiN(SO₂CF₃)₂ (Aldrich), 47 mM 4-t-butylpyridine(Aldrich) in chlorobenzene was made up.

At 0.1 sun and 1 sun, the short-circuit current densities I_(SC) were0.42 mA/cm² and 4.39 mA/cm² respectively, the terminal voltages V_(OC)with an open circuit 0.78 V and 0.84 V respectively, the fill factors(FF) 68% and 54% respectively, and the efficiencies 2.3% and 2.0%respectively.

Comparative Example DSC 11

As described in example DSC 10, a solid DSC was produced with the holeconductor spiro-MeO-TAD and the dye perylene 2 (dye bath: 0.5 mMsolution of the dye perylene 2 in dichloromethane). For this purpose, asolution of 123 mM spiro-MeO-TAD, 11 mM LiN(SO₂CF₃)₂ (Aldrich), 45 mM4-t-butylpyridine (Aldrich) in chlorobenzene was made up.

At 0.1 sun and 1 sun, the short-circuit current densities l_(SC) were0.52 mA/cm² and 6.87 mA/cm² respectively, the terminal voltages V_(OC)with an open circuit 0.74 V and 0.76 V respectively, the fill factors(FF) 70% and 56% respectively, and the efficiencies 2.7% and 2.9%respectively.

DSC 12:

As described in example DSC 1, a solid DSC was produced with the holeconductor ID523 and the dye perylene 3 (dye bath: 0.5 mM solution of thedye perylene 3 in dichloromethane). For this purpose, a solution of 214mM ID523, 19 mM LiN(SO₂CF₃)₂ (Aldrich), 78 mM 4-t-butylpyridine(Aldrich) in chlorobenzene was made up. The thickness of the nanoporousTiO₂ layer was approx. 3.1 μm instead of approx. 1.8 μm.

At 0.1 sun and 1 sun, the short-circuit current densities I_(SC) were0.21 mA/cm² and 3.40 mA/cm² respectively, the terminal voltages V_(OC)with an open circuit 0.64 V and 0.66 V respectively, the fill factors(FF) 64% and 59% respectively, and the efficiencies 0.9% and 1.3%respectively.

Comparative Example DSC 12

As described in example DSC 12, a solid DSC was produced with the holeconductor spiro-MeO-TAD and the dye perylene 3 (dye bath: 0.5 mMsolution of the dye perylene 3 in dichloromethane). For this purpose, asolution of 204 mM spiro-MeO-TAD, 19 mM LiN(SO₂CF₃)₂ (Aldrich), 74 mM4-t-butylpyridine (Aldrich) in chlorobenzene was made up. The thicknessof the nanoporous TiO₂ layer was approx. 3.1 μm instead of approx. 1.8μm.

At 0.1 sun and 1 sun, the short-circuit current densities I_(SC) were0.25 mA/cm² and 3.97 mA/cm² respectively, the terminal voltages V_(OC)with an open circuit 0.62 V and 0.66 V respectively, the fill factors(FF) 66% and 57% respectively, and the efficiencies 1.0% and 1.5%respectively.

1. A hole-conducting material comprising a compound of general formula I

in which A¹, A², A³ are each independently divalent organic units whichmay comprise one, two or three optionally substituted aromatic orheteroaromatic groups, where, in the case of two or three aromatic orheteroaromatic groups, two of these groups in each case are joined toone another by a chemical bond and/or via a divalent alkyl radical, R¹,R², R³ are each independently R, OR, NR₂, A³-OR or A³-NR₂ substituents,R is alkyl, aryl or a monovalent organic radical which may comprise one,two or three optionally substituted aromatic or heteroaromatic groups,where, in the case of two or three aromatic or heteroaromatic groups,two of these groups in each case are joined to one another by a chemicalbond and/or via a divalent alkyl or NR′ radical, R′ is alkyl, aryl or amonovalent organic radical which may comprise one, two or threeoptionally substituted aromatic or heteroaromatic groups, where, in thecase of two or three aromatic or heteroaromatic groups, two of thesegroups in each case are joined to one another by a chemical bond and/orvia a divalent alkyl radical, and n at each instance in formula I isindependently 0, 1, 2 or 3, wherein the sum of the individual values nis at least 2 and at least two of the R¹, R² and R³ radicals are ORand/or NR₂ substituents. as hole conducting materials in organic solarcells.
 2. The hole-conducting material comprising the compound accordingto claim 1, wherein at least two of the R¹, R² and R³ radicals arepara-OR and/or -NR₂ substituents.
 3. The hole-conducting materialcomprising the compound according to claim 1, wherein at least four ofthe R¹, R² and R³ radicals are para-OR and/or -NR₂ substituents.
 4. Thehole-conducting material comprising the compound according to claim 1,wherein all of the R¹, R² and R³ radicals are para-OR and/or —NR₂substituents.
 5. The hole-conducting material comprising the compoundaccording to claim 1, wherein the organic A¹, A² and A³ units areselected from the group consisting of (CH₂)_(m), C(R⁷)(R⁸), N(R⁹),

in which m is an integer from 1 to 18, R⁴, R⁹ are each alkyl, aryl or amonovalent organic radical which may comprise one, two or threeoptionally substituted aromatic or heteroaromatic groups, where, in thecase of two or three aromatic or heteroaromatic groups, two of thesegroups in each case are joined to one another by a chemical bond and/orvia a divalent alkyl radical, R⁵, R⁶, R⁷, R⁸ are each independentlyhydrogen atoms or radicals as defined for R⁴ and R⁹, and the aromaticand heteroaromatic rings of the units shown may have furthersubstitution.
 6. The hole-conducting material comprising the compoundaccording to claim 1, wherein R in the R¹, R² and R³ radicals isindependently C₁- to C₈-alkyl, cyclopentyl, cyclohexyl or aryl. 7.(canceled)
 8. An organic solar cell comprising a compound of generalformula I

in which A¹, A², A³ are each independently divalent organic units whichmay comprise one, two or three optionally substituted aromatic orheteroaromatic groups, where, in the case of two or three aromatic orheteroaromatic groups, two of these groups in each case are joined toone another by a chemical bond and/or via a divalent alkyl radical, R¹,R², R³ are each independently R, OR, NR₂, A³-OR or A³-NR₂ substituents,R is alkyl, aryl or a monovalent organic radical which may comprise one,two or three optionally substituted aromatic or heteroaromatic groups,where, in the case of two or three aromatic or heteroaromatic groups,two of these groups in each case are joined to one another by a chemicalbond and/or via a divalent alkyl or NR′ radical, R′ is alkyl, aryl or amonovalent organic radical which may comprise one, two or threeoptionally substituted aromatic or heteroaromatic groups, where, in thecase of two or three aromatic or heteroaromatic groups, two of thesegroups in each case are joined to one another by a chemical bond and/orvia a divalent alkyl radical, and n at each instance in formula I isindependently 0, 1, 2 or 3, wherein the sum of the individual values nis at least 2 and at least two of the R¹, R² and R³ radicals are ORand/or NR₂ substituents.
 9. The organic solar cell according to claim 8,wherein in the compound at least two of the R¹, R² and R³ radicals arepara-OR and/or -NR₂ substituents.
 10. The organic solar cell accordingto claim 8, wherein in the compound at least four of the R¹, R² and R³radicals are para-OR and/or -NR₂ substituents.
 11. The organic solarcell according to claim 8, wherein in the compound all of the R¹, R² andR³ radicals are para-OR and/or -NR₂ substituents.
 12. The organic solarcell according to claim 8, wherein in the compound the organic A¹, A²and A³ units are selected from the group consisting of (CH₂)_(m),C(R⁷)(R⁸), N(R⁹),

in which m is an integer from 1 to 18, R⁴, R⁹ are each alkyl, aryl or amonovalent organic radical which may comprise one, two or threeoptionally substituted aromatic or heteroaromatic groups, where, in thecase of two or three aromatic or heteroaromatic groups, two of thesegroups in each case are joined to one another by a chemical bond and/orvia a divalent alkyl radical, R⁵, R⁶, R⁷, R⁸ are each independentlyhydrogen atoms or radicals as defined for R⁴ and R⁹, and the aromaticand heteroaromatic rings of the units shown may have furthersubstitution.
 13. The organic solar cell according to claim 8, whereinin the compound R in the R¹, R² and R³ radicals is independently C₁- toC₈-alkyl, cyclopentyl, cyclohexyl or aryl.
 14. The organic solar cellaccording to claim 8, wherein the solar cell comprises a plurality oflayers, and one of said layers is a hole-conducting material layercomprising the compound.